Center tile objects at the mouse on insertion

This fixes mapeditor#67 without changing the TMX map format.

This means the bottom-left remains the origin of the tile objects even
though plain rectangle objects have their origin in the top-left. This
difference was the reason for the wrong positioning of tile objects when
inserting them, which is now fixed by taking the difference into account
in the Insert Tile Objects tool. The tool now centers the inserted tile
object at the mouse position.

The reason tile objects have their origin in the bottom-left is because
tiles in tile layers are also bottom-left aligned within their grid
cell. This in turn has its origins in top-down maps where this behavior
is usually desirable when working with tile images that are larger than
the grid size.

NEWS

@@ -4,6 +4,7 @@
 * Small improvement to the Lua export plugin (incompatible!)
 * Fixed a bug in the Create Object tool
 * Fixed reading of maps without tilesets but with a tile layer
+* Fixed position of tile objects to center on the mouse on insertion
 * Updated the Czech translation
 
 0.7.0 (20 July 2011)

src/libtiled/tile.h

@@ -77,6 +77,11 @@ class TILEDSHARED_EXPORT Tile : public Object
      */
     int height() const { return mImage.height(); }
 
+    /**
+     * Returns the size of this tile.
+     */
+    QSize size() const { return mImage.size(); }
+
 private:
     int mId;
     Tileset *mTileset;

src/tiled/createobjecttool.cpp

@@ -81,13 +81,14 @@ void CreateObjectTool::mouseMoved(const QPointF &pos,
         return;
 
     const MapRenderer *renderer = mapDocument()->renderer();
-    QPointF tileCoords = renderer->pixelToTileCoords(pos);
 
     bool snapToGrid = Preferences::instance()->snapToGrid();
     if (modifiers & Qt::ControlModifier)
         snapToGrid = !snapToGrid;
 
     if (mMode == AreaObjects) {
+        const QPointF tileCoords = renderer->pixelToTileCoords(pos);
+
         // Update the size of the new map object
         const QPointF objectPos = mNewMapObjectItem->mapObject()->position();
         QSizeF newSize(qMax(qreal(0), tileCoords.x() - objectPos.x()),
@@ -98,6 +99,10 @@ void CreateObjectTool::mouseMoved(const QPointF &pos,
 
         mNewMapObjectItem->resize(newSize);
     } else {
+        const QSize imgSize = mNewMapObjectItem->mapObject()->tile()->size();
+        const QPointF diff(-imgSize.width() / 2, imgSize.height() / 2);
+        QPointF tileCoords = renderer->pixelToTileCoords(pos + diff);
+
         if (snapToGrid)
             tileCoords = tileCoords.toPoint();
 
@@ -121,19 +126,30 @@ void CreateObjectTool::mousePressed(QGraphicsSceneMouseEvent *event)
     }
 
     ObjectGroup *objectGroup = currentObjectGroup();
-    if (objectGroup && objectGroup->isVisible() && !mNewMapObjectItem) {
-        const MapRenderer *renderer = mapDocument()->renderer();
-        QPointF tileCoords = renderer->pixelToTileCoords(event->scenePos());
+    if (!objectGroup || !objectGroup->isVisible())
+        return;
 
-        bool snapToGrid = Preferences::instance()->snapToGrid();
-        if (event->modifiers() & Qt::ControlModifier)
-            snapToGrid = !snapToGrid;
+    const MapRenderer *renderer = mapDocument()->renderer();
+    QPointF tileCoords;
 
-        if (snapToGrid)
-            tileCoords = tileCoords.toPoint();
+    if (mMode == AreaObjects) {
+        tileCoords = renderer->pixelToTileCoords(event->scenePos());
+    } else {
+        if (!mTile)
+            return;
 
-        startNewMapObject(tileCoords, objectGroup);
+        const QPointF diff(-mTile->width() / 2, mTile->height() / 2);
+        tileCoords = renderer->pixelToTileCoords(event->scenePos() + diff);
     }
+
+    bool snapToGrid = Preferences::instance()->snapToGrid();
+    if (event->modifiers() & Qt::ControlModifier)
+        snapToGrid = !snapToGrid;
+
+    if (snapToGrid)
+        tileCoords = tileCoords.toPoint();
+
+    startNewMapObject(tileCoords, objectGroup);
 }
 
 void CreateObjectTool::mouseReleased(QGraphicsSceneMouseEvent *event)